// SPDX-License-Identifier: GPL-2.0-only
/*
* Connection tracking protocol helper module for GRE.
*
* GRE is a generic encapsulation protocol, which is generally not very
* suited for NAT, as it has no protocol-specific part as port numbers.
*
* It has an optional key field, which may help us distinguishing two
* connections between the same two hosts.
*
* GRE is defined in RFC 1701 and RFC 1702, as well as RFC 2784
*
* PPTP is built on top of a modified version of GRE, and has a mandatory
* field called "CallID", which serves us for the same purpose as the key
* field in plain GRE.
*
* Documentation about PPTP can be found in RFC 2637
*
* (C) 2000-2005 by Harald Welte <[email protected]>
*
* Development of this code funded by Astaro AG (http://www.astaro.com/)
*
* (C) 2006-2012 Patrick McHardy <[email protected]>
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/list.h>
#include <linux/seq_file.h>
#include <linux/in.h>
#include <linux/netdevice.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/dst.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_timeout.h>
#include <linux/netfilter/nf_conntrack_proto_gre.h>
#include <linux/netfilter/nf_conntrack_pptp.h>
static const unsigned int gre_timeouts[GRE_CT_MAX] = {
[GRE_CT_UNREPLIED] = 30*HZ,
[GRE_CT_REPLIED] = 180*HZ,
};
/* used when expectation is added */
static DEFINE_SPINLOCK(keymap_lock);
static inline struct nf_gre_net *gre_pernet(struct net *net)
{
return &net->ct.nf_ct_proto.gre;
}
static inline int gre_key_cmpfn(const struct nf_ct_gre_keymap *km,
const struct nf_conntrack_tuple *t)
{
return km->tuple.src.l3num == t->src.l3num &&
!memcmp(&km->tuple.src.u3, &t->src.u3, sizeof(t->src.u3)) &&
!memcmp(&km->tuple.dst.u3, &t->dst.u3, sizeof(t->dst.u3)) &&
km->tuple.dst.protonum == t->dst.protonum &&
km->tuple.dst.u.all == t->dst.u.all;
}
/* look up the source key for a given tuple */
static __be16 gre_keymap_lookup(struct net *net, struct nf_conntrack_tuple *t)
{
struct nf_gre_net *net_gre = gre_pernet(net);
struct nf_ct_gre_keymap *km;
__be16 key = 0;
list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
if (gre_key_cmpfn(km, t)) {
key = km->tuple.src.u.gre.key;
break;
}
}
pr_debug("lookup src key 0x%x for ", key);
nf_ct_dump_tuple(t);
return key;
}
/* add a single keymap entry, associate with specified master ct */
int nf_ct_gre_keymap_add(struct nf_conn *ct, enum ip_conntrack_dir dir,
struct nf_conntrack_tuple *t)
{
struct net *net = nf_ct_net(ct);
struct nf_gre_net *net_gre = gre_pernet(net);
struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
struct nf_ct_gre_keymap **kmp, *km;
kmp = &ct_pptp_info->keymap[dir];
if (*kmp) {
/* check whether it's a retransmission */
list_for_each_entry_rcu(km, &net_gre->keymap_list, list) {
if (gre_key_cmpfn(km, t) && km == *kmp)
return 0;
}
pr_debug("trying to override keymap_%s for ct %p\n",
dir == IP_CT_DIR_REPLY ? "reply" : "orig", ct);
return -EEXIST;
}
km = kmalloc(sizeof(*km), GFP_ATOMIC);
if (!km)
return -ENOMEM;
memcpy(&km->tuple, t, sizeof(*t));
*kmp = km;
pr_debug("adding new entry %p: ", km);
nf_ct_dump_tuple(&km->tuple);
spin_lock_bh(&keymap_lock);
list_add_tail(&km->list, &net_gre->keymap_list);
spin_unlock_bh(&keymap_lock);
return 0;
}
EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_add);
/* destroy the keymap entries associated with specified master ct */
void nf_ct_gre_keymap_destroy(struct nf_conn *ct)
{
struct nf_ct_pptp_master *ct_pptp_info = nfct_help_data(ct);
enum ip_conntrack_dir dir;
pr_debug("entering for ct %p\n", ct);
spin_lock_bh(&keymap_lock);
for (dir = IP_CT_DIR_ORIGINAL; dir < IP_CT_DIR_MAX; dir++) {
if (ct_pptp_info->keymap[dir]) {
pr_debug("removing %p from list\n",
ct_pptp_info->keymap[dir]);
list_del_rcu(&ct_pptp_info->keymap[dir]->list);
kfree_rcu(ct_pptp_info->keymap[dir], rcu);
ct_pptp_info->keymap[dir] = NULL;
}
}
spin_unlock_bh(&keymap_lock);
}
EXPORT_SYMBOL_GPL(nf_ct_gre_keymap_destroy);
/* PUBLIC CONNTRACK PROTO HELPER FUNCTIONS */
/* gre hdr info to tuple */
bool gre_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
struct net *net, struct nf_conntrack_tuple *tuple)
{
const struct pptp_gre_header *pgrehdr;
struct pptp_gre_header _pgrehdr;
__be16 srckey;
const struct gre_base_hdr *grehdr;
struct gre_base_hdr _grehdr;
/* first only delinearize old RFC1701 GRE header */
grehdr = skb_header_pointer(skb, dataoff, sizeof(_grehdr), &_grehdr);
if (!grehdr || (grehdr->flags & GRE_VERSION) != GRE_VERSION_1) {
/* try to behave like "nf_conntrack_proto_generic" */
tuple->src.u.all = 0;
tuple->dst.u.all = 0;
return true;
}
/* PPTP header is variable length, only need up to the call_id field */
pgrehdr = skb_header_pointer(skb, dataoff, 8, &_pgrehdr);
if (!pgrehdr)
return true;
if (grehdr->protocol != GRE_PROTO_PPP) {
pr_debug("Unsupported GRE proto(0x%x)\n", ntohs(grehdr->protocol));
return false;
}
tuple->dst.u.gre.key = pgrehdr->call_id;
srckey = gre_keymap_lookup(net, tuple);
tuple->src.u.gre.key = srckey;
return true;
}
#ifdef CONFIG_NF_CONNTRACK_PROCFS
/* print private data for conntrack */
static void gre_print_conntrack(struct seq_file *s, struct nf_conn *ct)
{
seq_printf(s, "timeout=%u, stream_timeout=%u ",
(ct->proto.gre.timeout / HZ),
(ct->proto.gre.stream_timeout / HZ));
}
#endif
static unsigned int *gre_get_timeouts(struct net *net)
{
return gre_pernet(net)->timeouts;
}
/* Returns verdict for packet, and may modify conntrack */
int nf_conntrack_gre_packet(struct nf_conn *ct,
struct sk_buff *skb,
unsigned int dataoff,
enum ip_conntrack_info ctinfo,
const struct nf_hook_state *state)
{
unsigned long status;
if (!nf_ct_is_confirmed(ct)) {
unsigned int *timeouts = nf_ct_timeout_lookup(ct);
if (!timeouts)
timeouts = gre_get_timeouts(nf_ct_net(ct));
/* initialize to sane value. Ideally a conntrack helper
* (e.g. in case of pptp) is increasing them */
ct->proto.gre.stream_timeout = timeouts[GRE_CT_REPLIED];
ct->proto.gre.timeout = timeouts[GRE_CT_UNREPLIED];
}
status = READ_ONCE(ct->status);
/* If we've seen traffic both ways, this is a GRE connection.
* Extend timeout. */
if (status & IPS_SEEN_REPLY) {
nf_ct_refresh_acct(ct, ctinfo, skb,
ct->proto.gre.stream_timeout);
/* never set ASSURED for IPS_NAT_CLASH, they time out soon */
if (unlikely((status & IPS_NAT_CLASH)))
return NF_ACCEPT;
/* Also, more likely to be important, and not a probe. */
if (!test_and_set_bit(IPS_ASSURED_BIT, &ct->status))
nf_conntrack_event_cache(IPCT_ASSURED, ct);
} else
nf_ct_refresh_acct(ct, ctinfo, skb,
ct->proto.gre.timeout);
return NF_ACCEPT;
}
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_cttimeout.h>
static int gre_timeout_nlattr_to_obj(struct nlattr *tb[],
struct net *net, void *data)
{
unsigned int *timeouts = data;
struct nf_gre_net *net_gre = gre_pernet(net);
if (!timeouts)
timeouts = gre_get_timeouts(net);
/* set default timeouts for GRE. */
timeouts[GRE_CT_UNREPLIED] = net_gre->timeouts[GRE_CT_UNREPLIED];
timeouts[GRE_CT_REPLIED] = net_gre->timeouts[GRE_CT_REPLIED];
if (tb[CTA_TIMEOUT_GRE_UNREPLIED]) {
timeouts[GRE_CT_UNREPLIED] =
ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_UNREPLIED])) * HZ;
}
if (tb[CTA_TIMEOUT_GRE_REPLIED]) {
timeouts[GRE_CT_REPLIED] =
ntohl(nla_get_be32(tb[CTA_TIMEOUT_GRE_REPLIED])) * HZ;
}
return 0;
}
static int
gre_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
{
const unsigned int *timeouts = data;
if (nla_put_be32(skb, CTA_TIMEOUT_GRE_UNREPLIED,
htonl(timeouts[GRE_CT_UNREPLIED] / HZ)) ||
nla_put_be32(skb, CTA_TIMEOUT_GRE_REPLIED,
htonl(timeouts[GRE_CT_REPLIED] / HZ)))
goto nla_put_failure;
return 0;
nla_put_failure:
return -ENOSPC;
}
static const struct nla_policy
gre_timeout_nla_policy[CTA_TIMEOUT_GRE_MAX+1] = {
[CTA_TIMEOUT_GRE_UNREPLIED] = { .type = NLA_U32 },
[CTA_TIMEOUT_GRE_REPLIED] = { .type = NLA_U32 },
};
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
void nf_conntrack_gre_init_net(struct net *net)
{
struct nf_gre_net *net_gre = gre_pernet(net);
int i;
INIT_LIST_HEAD(&net_gre->keymap_list);
for (i = 0; i < GRE_CT_MAX; i++)
net_gre->timeouts[i] = gre_timeouts[i];
}
/* protocol helper struct */
const struct nf_conntrack_l4proto nf_conntrack_l4proto_gre = {
.l4proto = IPPROTO_GRE,
.allow_clash = true,
#ifdef CONFIG_NF_CONNTRACK_PROCFS
.print_conntrack = gre_print_conntrack,
#endif
#if IS_ENABLED(CONFIG_NF_CT_NETLINK)
.tuple_to_nlattr = nf_ct_port_tuple_to_nlattr,
.nlattr_tuple_size = nf_ct_port_nlattr_tuple_size,
.nlattr_to_tuple = nf_ct_port_nlattr_to_tuple,
.nla_policy = nf_ct_port_nla_policy,
#endif
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
.ctnl_timeout = {
.nlattr_to_obj = gre_timeout_nlattr_to_obj,
.obj_to_nlattr = gre_timeout_obj_to_nlattr,
.nlattr_max = CTA_TIMEOUT_GRE_MAX,
.obj_size = sizeof(unsigned int) * GRE_CT_MAX,
.nla_policy = gre_timeout_nla_policy,
},
#endif /* CONFIG_NF_CONNTRACK_TIMEOUT */
};
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